valve Meaning, Definition & Usage

noun a structure in a hollow organ (like the heart) with a flap to insure one-way flow of fluid through it
noun device in a brass wind instrument for varying the length of the air column to alter the pitch of a tone
noun control consisting of a mechanical device for controlling the flow of a fluid
noun the entire one-piece shell of a snail and certain other molluscs
noun one of the paired hinged shells of certain molluscs and of brachiopods

L. valva the leaf, fold, or valve of a door: cf. F. valve.

A door; especially, one of a pair of folding doors, or one of the leaves of such a door.
Swift through the valves the visionary fair Repassed. Pope.

Heavily closed, . . . the valves of the barn doors. Longfellow.
A lid, plug, or cover, applied to an aperture so that by its movement, as by swinging, lifting and falling, sliding, turning, or the like, it will open or close the aperture to permit or prevent passage, as of a fluid. ✍ A valve may act automatically so as to be opened by the effort of a fluid to pass in one direction, and closed by the effort to pass in the other direction, as a clack valve; or it may be opened or closed by hand or by mechanism, as a screw valve, or a slide valve.
(Anat.) One or more membranous partitions, flaps, or folds, which permit the passage of the contents of a vessel or cavity in one direction, but stop or retard the flow in the opposite direction; as, the ileocolic, mitral, and semilunar valves.
(Bot.) (a) One of the pieces into which a capsule naturally separates when it bursts. (b) One of the two similar portions of the shell of a diatom. (c) A small portion of certain anthers, which opens like a trapdoor to allow the pollen to escape, as in the barberry.
(Zoöl.) One of the pieces or divisions of bivalve or multivalve shells.